1. Technical Field
Embodiments of the present invention relate to a charger positioning adjuster to position a charger that uniformly charges a surface of an image carrier, and an electrophotographic image forming apparatus incorporating the charger positioning adjuster.
2. Related Art
Corona chargers or chargers using a corona discharging technique are known to uniformly charge a surface of an image carrier that is included in an electrophotographic image forming apparatus. The corona chargers are good for high-speed apparatuses for its wider range of application of a charging bias in comparison with those of a charging roller and a charging brush. Compared with low-speed or middle-speed apparatuses, typical high-speed apparatuses are requested to provide higher image quality, and therefore are demanded to have a higher level with respect to deviation in image concentration in a main scanning direction that is a longitudinal direction of the charger. To enhance the deviation of image concentration in the main scanning direction, various configurations have been disclosed to prevent occurrence of deviation of a surface potential of the image carrier in a main scanning direction by reducing the deviation of the distance between a corona charger and the image carrier in the main scanning direction. For example, Japanese Patent Application Publication JP H03-101767-A discloses a technique to automatically control a deviation of a distance between a charger and an image carrier by using an electric drive source in order to reduce the deviation of surface electric potentials after charging a surface of the image carrier.
Since the deviation of distances between the corona charger and the image carrier in the main scanning direction occurs due to variation of parts and/or assembly, it is less likely to cause fluctuation of the distances while the image forming apparatus is in operation.
Appropriate timing to adjust the deviation of the distances of the corona charger and the image carrier in the main scanning direction is before the factory shipping and/or at replacement of a corona charger. When the corona charger is integrally provided with a process cartridge, the deviation of the distances of the charger and the image carrier is also adjusted at replacement of the process cartridge.
Thus, if an electric drive source is used as disclosed in JP H03-101767-A, the deviation can be reduced even though the image forming apparatus is not used often. However, this configuration also requires an installation space and a drive transmission system to transmit a driving force of the electric drive source to the charger. Therefore, the configuration can be improved in order to achieve a simpler and more space-saving configuration.